Just upgraded OS 6 on my Bold 9780 to version (bundle) 1965.
The "C" shortcut for "compose" now activates the search bar from within the messages inbox. Is it a bug or a deliberate change ?

Go into Options / Display / Home Screen Preferences

Make sure that "Launch by Typing" is set to "Application Shortcuts"

See if that helps.

Not sure anyone would know if its a deliberate change except RIM.

Unfortunately it didn't.
Now "C" launches the Contacts application and obviously eliminates the very useful Search feature on Home screen.
I suspect it was a deliberate change by RIM, knowing that, for that purpose, you can always use the "compose" option within the messages menu.

Some people prefer the shortcuts on the homescreen.
I have the 9700 - clearly not the 9780 - and the "C" (Compose) still works in the messages folder in a newer bundle. Perhaps it is a bug that will be cleared up in a later version.

I believe you are right, unless RIM decided that "C" is more useful for searching, within the messages inbox. "T" and "B" still work ok.

This is really funny: I launched Desktop Software, backed up settings and data, removed Opera Mini and now.... the "C" shortcut works flawlessly from within the messages inbox, both for text and emails. Wonder what happened.
All's well that ends well.
Thanks to all.